In electronic components mounting apparatuses, such as electronic component placing apparatuses used in electronic component mounting lines, in order to identify substrates or detect the positions of the substrates, a camera is used to capture the image of an object to be recognized, such as an identification mark provided on the surface of the substrate. During an image capturing process, a lighting device emits illumination light to the surface of the substrate, and a camera receives light reflected from an object to be recognized, thereby capturing the image of the object to be recognized.
In general, reflection characteristics of reflecting illumination light depend on the surface properties or states of objects to be recognized. Therefore, in order to enable the camera to receive good reflected light during an image capturing process, the following structure has been proposed in which a plurality of light sources forming a lighting device are disposed at different positions and the emission angle of illumination light to the surface of the substrate can be changed according to objects to be recognized (for example, see Patent Document 1). In the structure disclosed in Patent Document 1, a plurality of lighting substrates each having LEDs, serving as light sources, arranged in a ring shape thereon are laminated in the vertical direction, and thus the light sources emit illumination light components to the substrate, which is an object whose image is to be captured, at different emission angles in plural directions.
Patent Document 1
JP-A-2003-168899